Text

Text

A React component for displaying text.

Text supports nesting, styling, and touch handling.

In the following example, the nested title and body text will inherit the fontFamily from styles.baseText, but the title provides its own additional styles. The title and body will stack on top of each other on account of the literal newlines:

import React, { Component } from 'react';
import { AppRegistry, Text, StyleSheet } from 'react-native';

export default class TextInANest extends Component {
  constructor(props) {
    super(props);
    this.state = {
      titleText: "Bird's Nest",
      bodyText: 'This is not really a bird nest.'
    };
  }

  render() {
    return (
      <Text style={styles.baseText}>
        <Text style={styles.titleText} onPress={this.onPressTitle}>
          {this.state.titleText}{'\n'}{'\n'}
        </Text>
        <Text numberOfLines={5}>
          {this.state.bodyText}
        </Text>
      </Text>
    );
  }
}

const styles = StyleSheet.create({
  baseText: {
    fontFamily: 'Cochin',
  },
  titleText: {
    fontSize: 20,
    fontWeight: 'bold',
  },
});

// skip this line if using Create React Native App
AppRegistry.registerComponent('TextInANest', () => TextInANest);

Props

accessible?: PropTypes.bool

When set to true, indicates that the view is an accessibility element. The default value for a Text element is true.

See the Accessibility guide for more information.

allowFontScaling?: PropTypes.bool

Specifies whether fonts should scale to respect Text Size accessibility settings. The default is true.

ellipsizeMode?: PropTypes.oneOf(['head', 'middle', 'tail', 'clip'])

When numberOfLines is set, this prop defines how text will be truncated. numberOfLines must be set in conjunction with this prop.

This can be one of the following values:

• head - The line is displayed so that the end fits in the container and the missing text at the beginning of the line is indicated by an ellipsis glyph. e.g., "...wxyz"
• middle - The line is displayed so that the beginning and end fit in the container and the missing text in the middle is indicated by an ellipsis glyph. "ab...yz"
• tail - The line is displayed so that the beginning fits in the container and the missing text at the end of the line is indicated by an ellipsis glyph. e.g., "abcd..."
• clip - Lines are not drawn past the edge of the text container.

The default is tail.

clip is working only for iOS

numberOfLines?: PropTypes.number

Used to truncate the text with an ellipsis after computing the text layout, including line wrapping, such that the total number of lines does not exceed this number.

This prop is commonly used with ellipsizeMode.

onLayout?: PropTypes.func

Invoked on mount and layout changes with

{nativeEvent: {layout: {x, y, width, height}}}

onLongPress?: PropTypes.func

This function is called on long press.

e.g., onLongPress={this.increaseSize}>

onPress?: PropTypes.func

This function is called on press.

e.g., onPress={() => console.log('1st')}

pressRetentionOffset?: {top: number, left: number, bottom: number, right: number}

When the scroll view is disabled, this defines how far your touch may move off of the button, before deactivating the button. Once deactivated, try moving it back and you'll see that the button is once again reactivated! Move it back and forth several times while the scroll view is disabled. Ensure you pass in a constant to reduce memory allocations.

selectable?: PropTypes.bool

Lets the user select text, to use the native copy and paste functionality.

style?: style

testID?: PropTypes.string

Used to locate this view in end-to-end tests.

androiddisabled?: PropTypes.bool

Specifies the disabled state of the text view for testing purposes

androidnativeID?: PropTypes.string

Used to locate this view from native code.

androidselectionColor?: color

The highlight color of the text.

androidtextBreakStrategy?: PropTypes.oneOf(['simple', 'highQuality', 'balanced'])

Set text break strategy on Android API Level 23+, possible values are simple, highQuality, balanced The default value is highQuality.

iosadjustsFontSizeToFit?: PropTypes.bool

Specifies whether font should be scaled down automatically to fit given style constraints.

iosminimumFontScale?: PropTypes.number

Specifies smallest possible scale a font can reach when adjustsFontSizeToFit is enabled. (values 0.01-1.0).

iossuppressHighlighting?: PropTypes.bool

When true, no visual change is made when text is pressed down. By default, a gray oval highlights the text on press down.

Description

Nested Text

Both iOS and Android allow you to display formatted text by annotating ranges of a string with specific formatting like bold or colored text (NSAttributedString on iOS, SpannableString on Android). In practice, this is very tedious. For React Native, we decided to use web paradigm for this where you can nest text to achieve the same effect.

import React, { Component } from 'react';
import { AppRegistry, Text } from 'react-native';

export default class BoldAndBeautiful extends Component {
  render() {
    return (
      <Text style={{fontWeight: 'bold'}}>
        I am bold
        <Text style={{color: 'red'}}>
          and red
        </Text>
      </Text>
    );
  }
}

// skip this line if using Create React Native App
AppRegistry.registerComponent('BoldAndBeautiful', () => BoldAndBeautiful);

Behind the scenes, React Native converts this to a flat NSAttributedString or SpannableString that contains the following information:

"I am bold and red"
0-9: bold
9-17: bold, red

Nested Views (iOS Only)

On iOS, you can nest views within your Text component. Here's an example:

import React, { Component } from 'react';
import { AppRegistry, Text, View } from 'react-native';

export default class BlueIsCool extends Component {
  render() {
    return (
      <Text>
        There is a blue square
        <View style={{width: 50, height: 50, backgroundColor: 'steelblue'}} />
        in between my text.
      </Text>
    );
  }
}

// skip this line if using Create React Native App
AppRegistry.registerComponent('BlueIsCool', () => BlueIsCool);

In order to use this feature, you must give the view a width and a height.

Containers

The <Text> element is special relative to layout: everything inside is no longer using the flexbox layout but using text layout. This means that elements inside of a <Text> are no longer rectangles, but wrap when they see the end of the line.

<Text>
  <Text>First part and </Text>
  <Text>second part</Text>
</Text>
// Text container: all the text flows as if it was one
// |First part |
// |and second |
// |part       |

<View>
  <Text>First part and </Text>
  <Text>second part</Text>
</View>
// View container: each text is its own block
// |First part |
// |and        |
// |second part|

Limited Style Inheritance

On the web, the usual way to set a font family and size for the entire document is to take advantage of inherited CSS properties like so:

/* CSS, *not* React Native */
html {
  font-family: 'lucida grande', tahoma, verdana, arial, sans-serif;
  font-size: 11px;
  color: #141823;
}

All elements in the document will inherit this font unless they or one of their parents specifies a new rule.

In React Native, we are more strict about it: you must wrap all the text nodes inside of a <Text> component; you cannot have a text node directly under a <View>.

// BAD: will raise exception, can't have a text node as child of a <View>
<View>
  Some text
</View>

// GOOD
<View>
  <Text>
    Some text
  </Text>
</View>

You also lose the ability to set up a default font for an entire subtree. The recommended way to use consistent fonts and sizes across your application is to create a component MyAppText that includes them and use this component across your app. You can also use this component to make more specific components like MyAppHeaderText for other kinds of text.

<View>
  <MyAppText>Text styled with the default font for the entire application</MyAppText>
  <MyAppHeaderText>Text styled as a header</MyAppHeaderText>
</View>

Assuming that MyAppText is a component that simply renders out its children into a Text component with styling, then MyAppHeaderText can be defined as follows:

class MyAppHeaderText extends Component {
  render() {
    <MyAppText>
      <Text style={{fontSize: 20}}>
        {this.props.children}
      </Text>
    </MyAppText>
  }
}

Composing MyAppText in this way ensures that we get the styles from a top-level component, but leaves us the ability to add / override them in specific use cases.

React Native still has the concept of style inheritance, but limited to text subtrees. In this case, the second part will be both bold and red.

<Text style={{fontWeight: 'bold'}}>
  I am bold
  <Text style={{color: 'red'}}>
    and red
  </Text>
</Text>

We believe that this more constrained way to style text will yield better apps:

• (Developer) React components are designed with strong isolation in mind: You should be able to drop a component anywhere in your application, trusting that as long as the props are the same, it will look and behave the same way. Text properties that could inherit from outside of the props would break this isolation.

• (Implementor) The implementation of React Native is also simplified. We do not need to have a fontFamily field on every single element, and we do not need to potentially traverse the tree up to the root every time we display a text node. The style inheritance is only encoded inside of the native Text component and doesn't leak to other components or the system itself.